print 'Hello, World.\n';
print "Hello, World.\n";
print "Hello, World.\n";

#When a string is enclosed in single quotes, all characters are
#treated as literals. When a string is enclosed in double quotes,
#however, almost all characters are treated as literals with the
#exception of those characters that are used for variable
#substitution and special escape sequences.

my $str  = "aBcDefg";
my $lStr = "\L$str\E";    #Change to lower case
my $uStr = "\U$str\E";    #Change to upper case
print "lStr: $lStr\n";
print "uStr: $uStr\n";

#\l Next character is converted to lowercase
#\u Next character is converted to uppercase
#\L Next characters are converted to lowercase until \E is found
#\U Next characters are converted to uppercase until \E is found
#\Q Backslash all following nonalphanumeric characters until \E is found
#\E Ends upper- or lowercase conversion started with \L or \U
#\\ Backslash

# Using quote-like operators.
print 'She cried, "I can\'t help you!"', "\n";    # Clumsy
print qq/She cried, "I can't help you!"\n/; # qq for double
                                            # quotes
print qq(I need $5.00\n);                   # Really need single quotes
                                            # for a literal dollar sign to print
print q/I need $5.00\n/;      # What about backslash interpretation?
print qq(I need \$5.00\n);    # Can escape the dollar sign
print qq/\n/, q/I need $5.00/, "\n";
print q!I need $5.00!, "\n";
print "The present working directory is ", 'pwd', "\n";

#print qq/Today is /, qx/date/;
#print "The hour is ", qx{date +%H};

my $num = 100;
print "here are some operations on $num",
  $num + 100, $num * 2, $num / 4,
  "endl.\n";

  
printf "%05d%05d%05d\n", $num, $num, $num;
printf "%5d%5d%5d\n", $num, $num, $num;  